Q1. [3] medium thorough-understanding
A child's diet is consistently deficient in iodine over several years. What visible symptom might develop, and what is the underlying chain of events — from missing nutrient to symptom — that produces it?
Generated by claude-sonnet-4-6 · 2026-06-26 01:02 · grounding rag
Model Answer
Visible symptom: Goitre — a swelling in the neck due to enlargement of the thyroid gland.
Chain of events:
- Iodine is essential for the thyroid gland to produce thyroxine hormone.
- When iodine is deficient in the diet, the thyroid gland cannot synthesise sufficient thyroxine.
- The thyroid gland keeps trying to compensate by growing larger, resulting in a visible swelling in the neck called goitre.
Using iodised salt in daily diet is the simplest way to prevent iodine deficiency.
Source: Life Processes, Chapter 5 (Control and Coordination cross-reference — standard CBSE Class 10 content on iodine deficiency)
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Explanation
- The question asks for two things: (1) the visible symptom and (2) the chain of events — so structure your answer in steps.
- Examiners expect the keyword goitre and the logical sequence: no iodine → no thyroxine → thyroid enlarges → goitre.
- Note: The source passages provided are from Chapters 1, 2, and 5 (digestion focus) and do not directly cover iodine/goitre. This topic comes from the Control and Coordination chapter. Since no passage covers it, the answer draws on standard CBSE textbook knowledge — examiners will expect the correct scientific chain as above.
- Keep it concise: name the symptom first, then list the steps clearly.